Homemade Bath Bombs?

Few questions! I've been thinking about making my own Halloween bath bombs. They'd be made in Halloween molds but I'd have scents like Root Beer and Cotton Candy and so forth if anyone was curious. Moving on! Questions!

1. Where can I get glitter or confetti that is safe for bath bombs?

2. Where can I get food coloring that is at least a dollar or no more than two?

3. Are stainless steel cookie cutters okay to use?

4. Does Cream of Tartar work better or worse than Citric Acid? Can't find Citric but there's a section in Walmart I heard that it can be found, just haven't checked.

5. Say I use a ghost cookie cutter or a mold that imprints a ghosts face, how do I paint the face on? Was thinking about just dyeing small parts of the soap and pressing it into place but that sounds dumb. Or I was thinking of using the frosting pens you can get at Walmart to paint the face but that doesn't sound good either.

I had more questions but these are all I can think of right now. Anything helps! Thank you!